Micromachining technology for lateral field emission devices

We demonstrate a range of novel applications of micromachining and microelectromechanical systems (MEMS) for achieving efficient and tunable field emission devices (FEDs). Arrays of lateral field emission tips are fabricated with submicron spacing utilizing deep reactive ion etch (DRIE). Current densities above 150 A/cm² are achieved with over 150·10⁶ tips/cm². With sacrificial sidewall spacing, electrodes can be placed at arbitrarily close distances to reduce turn-on voltages. We further utilize MEMS actuators to laterally adjust electrode distances. To improve the integration capability of FEDs, we demonstrate batch bump-transfer of working lateral FEDs onto a quartz target substrate     

Novel process for integration of optoelectronic devices using reactive ion etching without chlorinated gas

A new process for RIE of III?V compound semiconductors using mixtures of CH4, Ar and H2 as the etching gas is presented. This process can be successfully applied to most III-V materials used in micro-optoelectronic technology     

Deep reactive ion etching of thermally co-evaporated Te-Ge films for IR integrated optics components

Due to their remarkable transparency in the infrared region, telluride glasses are very promising materials for the realization of IR integrated optics components for specific applications, such as the detection of pollutant gases in the atmosphere or the detection of exoplanetary systems. In order to prove the feasibility of channel waveguiding structures based on this kind of materials, deep etching of thermally co-evaporated Te-Ge films, one of the most important and critical steps, was investigated. Reactive ion etching was carried out using different mixtures of three gases CHF₃, O₂ and Ar, and for different chamber pressures and RF powers. The influence of each parameter on the quality of etched Te-Ge films, in term of rib dimensions and surface roughness for example, was studied. Finally optimized parameters i.e. a CHF₃/O₂/Ar ratio of 59.5/10.5/30, a chamber pressure of 30 mTorr and a RF power of 50 W were used to fabricate a pattern showing the achievement in term of etching resolution.     

Neural network modeling of reactive ion etching using optical emission spectroscopy data

Neural networks are employed to model reactive ion etching (RIE) using optical emission spectroscopy (OES) data. While OES is an excellent tool for monitoring plasma emission intensity, a primary issue with its use is the large dimensionality of the spectroscopic data. To alleviate this concern, principal component analysis (PCA) and autoencoder neural networks (AENNs) are implemented as mechanisms for feature extraction to reduce the dimensionality of the OES data. OES data are generated from a 2/sup 4/ factorial experiment designed to characterize RIE process variation during the etching of benzocyclobutene (BCB) in a SF/sub 6//O/sub 2/ plasma, with controllable input factors consisting of the two gas flows, RF power, and chamber pressure. The OES data, consisting of 226 wavelengths sampled every 20 s, are compressed into five principal components using PCA and seven features using AENNs. Each method is subsequently used to establish multilayer perceptron neural networks trained using error back-propagation to model etch rate, uniformity, selectivity, and anisotropy. The neural network models of the etch responses using both methods show excellent agreement, with root-mean-squared errors as low as 0.215% between model predictions and measured data.     

耐反应离子刻蚀的紫外激光光致抗蚀剂的研究

以芳香族双迭氮基化合物为交联剂，苯氧基二苯甲酮为光敏剂，聚甲基丙烯酸甲酯（ＰＭＭＡ）为基质树脂，合成了负型激光光致抗蚀剂。该体系能够在氮分子激光辐照下发生灵敏的光致交联反应，所生成的致密薄膜可以耐四氟化碳等离子体的反应离子刻蚀（ＲＩＥ）。用付里叶变换红外光谱法与紫外光谱法研究了激光光致交联反应以及反应离子刻蚀的动力学过程。讨论了影响反应速率以及刻蚀选择比的诸因素。     

A novel etching technology with reactive ion etching system for GaAs via-hole etching applications

A via-hole dry etching technique has been studied with manipulating RF power and gas pressures in a reactive ion etching system. These parameters were optimized into a two-step recipe. With the recipe, a sloped and smooth profile can be obtained for monolithic microwave integrated circuits and power FET applications. With the two-step etching recipe, greater than 25:1 selectivity between GaAs/photoresist and less than 10% etching deviation were obtained. Furthermore, the slope angle from the horizontal surface is less than 80/spl deg/.     

硅传感器反应离子刻蚀的观察

六十年代发展起来的微电子技术,已大大影响了人类社会的面貌,而由微电子技术与机械学相互交叉而诞生的微机械技术,正成为一项新的产业。微电子技术以硅的平面加工技术为主,其制造工艺一般在表面几十微米以内。而微机械的厚度(或深度)往往达到几百微米,因此,必须研究硅的深加工技术以适应微机械的需求。本文以制作一种以玻璃为衬底的单晶硅叉指电容式加速度传感器为目的,开展了离子刻蚀技术的研究[1]。硅的反应离子刻蚀是一个复杂的辉光放电等离子体物理一化学作用过程。该技术早期存在刻蚀速率低,不能获得高的深宽比,掩膜选择比不高等技术障…     

Stencil-assisted reactive ion etching for micro and nano patterning

Stencil-assisted oxygen reactive ion etching is a low-cost and parallel process for the replication of micrometric and nanometric patterns in any organic material. This lithography process allows the patterning of organic material non sensitive to electronic or optical radiations, sensitive to solvents, or already patterned which cannot be patterned by conventional lithography methods. We demonstrate the versatility of stencil-assisted reactive ion etching though 3 examples. First to define 500 nm holes in PMMA. Secondly, the fabrication step has been integrated in a lift-off process of metal or molecular self-assembled monolayers. We finally apply stencil-assisted reactive ion etching to pattern an assembly of 100 nm latex nanoparticles.     

变结构反应离子刻蚀腔室流场热场的数值仿真

为了提高刻蚀的均匀性, 对400mm反应离子刻蚀(RIE)腔室建立了气体流动的连续流体模型和热传递模型, 研究了反应腔室内压强、流速和温度分布。冷却板恒温285K时, 依次改变入口流量和出口压强, 分别分析了腔室内部基片晶圆附近的流速、压强、温度的分布; 依次改变极板间距离(30mm~60mm)、进气口直径(300mm~620mm)、抽气口直径(50mm~250mm), 分析了反应腔室内气流和温度分布。结果表明, 压强分布呈现出边缘低中心高的特征, 流速呈现边缘高且中心低的特征, 且在小流量时压强的均匀性较好; 压强分布的均匀性随腔室极板间距离增加而有所提高, 且随腔室气体出口面积减小与进口面积增加也有所提高; 基片晶圆上方附近处温度场大面均匀、稳定, 几乎不受入口流量波动变化的影响, 热稳定性良好。该研究对大口径RIE腔室结构设计改进及对大口径反应离子刻蚀工艺控制具有重要意义。     

Via holes for GaAs MMICs fabricated using reactive ion etching

A dry etching process has been employed in the successful fabrication of through-substrate via holes for GaAs MMICs. The etching was carried out using Freon 12 (CCl2F2) as the etching gas. These vias have been shown to have low loss up to 12GHz.     

A system for precision reactive ion-beam etching of nanostructures for field-emission devices

An system for precision selective ion-beam etching of nanostructures for field-emission devices is developed. The system is equipped with a Radikal-M160 multibeam ion source with a cold cathode and closed electron drift forming the ion beam of the working substance with a diameter of 160 mm and a microwave input for the supply of the microwave bias to the treated substrates. Technological possibilities of the system are investigated experimentally. The advantages of simultaneous ion-beam and microwave etching of the nanostructures are shown. The processes of precision etching of nanostructures through a mask up to 1 μm thick with diameters of orifices of 20–30 nm (aspect ratio of the structures of the mask ∼50: 1) are carried out.     

Electron beam induced current investigations of active electrical defects in silicon due to reactive ion etching and reactive ion beam etching processes

Reactive ion etching and reactive ion beam etching are common tools for anisotropic etch processes in silicon microdevice fabrication; but, unfortunately, they also create radiation damage in the etched surface. We have studied the electrically active defects by measuring the recombination of carriers with the help of the electron beam induced current (EBIC) mode of a secondary electron microscope. We have measured the temperature behavior of the samples by annealing studies and the temperature dependent EBIC signal for several p-doped silicon wafers and obtained different shaped curves. Theoretical EBIC models developed with the assumption of a reduced net carrier concentration in the etched areas agree with our experimental results.     

Fabrication of sharp silicon tips employing anisotropic wet etching and reactive ion etching

We developed a process to obtain sharper silicon tips by employing anisotropic etching in a KOH solution followed by SF₆ plasma etch. The tips were further sharpened using the established thermal oxidation technique to decrease the cone angle and, therefore, obtain smaller curvature radii. We have analyzed the impact of such changes in geometry on a figure of merit associated with the field emission characteristics. An increase in the figure of merit by a factor of three was found in relation to the tips before sharpening.     

Real-time control of reactive ion etching using neural networks

This paper explores the use of neural networks for real-time, model-based feedback control of reactive ion etching (RIE). This objective is accomplished in part by constructing a predictive model for the system that can be approximately inverted to achieve the desired control. An indirect adaptive control (IAC) strategy is pursued. The IAC structure includes a controller and plant emulator, which are implemented as two separate back-propagation neural networks. These components facilitate nonlinear system identification and control, respectively. The neural network controller is applied to controlling the etch rate of a GaAs/AlGaAs metal-semiconductor-metal (MSM) structure in a BCl₃/Cl₂ plasma using a Plasma Therm 700 SLR series RIE system. Results indicate that in the presence of disturbances and shifts in RIE performance, the IAC neural controller is able to adjust the recipe to match the etch rate to that of the target value in less than 5 s. These results are shown to be superior to those of a more conventional control scheme using the linear quadratic Gaussian method with loop-transfer recovery, which is based on a linearized transfer function model of the RIE system     

Damage-free reactive ion etching of GaAs FET gate recess

A GaAs reactive ion etching process is described which has good uniformity and causes no significant electrical damage to the underlying substrate. The process is shown to be suitable for forming the gate recess of a GaAs MESFET. FETs fabricated using the process exhibit DC and RF performance similar to equivalent wet etched devices.<>     

反应离子刻蚀InSb芯片引入的损伤研究

应用CH₄/H₂/Ar作为刻蚀气源对InSb微台面阵列进行了反应离子刻蚀,并对刻蚀后引入的损伤进行了分析。实验证实利用干法刻蚀与湿法腐蚀相结合的方法能有效地减少刻蚀引入的缺陷和损伤,获得较好的电学特性,达到低损伤刻蚀InSb材料的目的。     

Time series modeling of reactive ion etching using neural networks

Neural networks have been used to model the behavior of real-time tool data in a reactive ion etch (RIE) process. An etch monitoring and data acquisition system for transferring data from the RIE chamber to a remote workstation was designed and implemented on a Plasma Therm Series 700 Dual Chamber etcher. This system monitors gas flow rates, RF power, temperature, pressure, and dc bias voltage. A neural network was trained on the monitored data using the feed-forward, error backpropagation algorithm. This network was used to perform three distinct modeling tasks. First, the network was trained on a subset of ten samples of the time series representing a single process run, and subsequently used to forecast the next data point. In the second task, the network was trained as in the first task, but used to predict the next ten values of the data sequence. In each of the first two tasks, the trained network yielded errors of less than 5%. In the final task, a neural net was used to generate a malfunction alarm when the sampled data did not conform to its previously established pattern     

Final polishing of Ga-polar GaN substrates using reactive ion etching

Reactive ion etching of {0001} oriented plate-like GaN single crystals has been investigated using SiCl₄:Ar:SF₆ chemistry. The reactive ion etching process is highly chemical. Large anisotropy of the etching rate and of the morphology has been established on (000 ) N-polar and (0001) Ga-polar sides of the GaN crystals, with remarkably higher rate on the N-polar side. Atomic force microscopy measurements have shown smooth surface and good polishing effect obtained on Ga-polar side, while N-polar surface exhibits an increased roughness of a factor of 10 after RIE.     

Iron nitride mask and reactive ion etching of GaN films

One of the major GaN processing challenges is useful pattern transfer. Serious photoresist mask erosion and hardening are often observed in reactive ion etching of GaN. Fine pattern transfer to GaN films using photoresist masks and complete removal of remaining photoresist after etching are very difficult. By replacing the etch mask from conventional photoresist to a sputtered iron nitride (Fe-8% N) film, which is easily patterned by wet chemical etching and is very resistive to Cl based plasmas, GaN films can be finely patterned with vertical etched sidewalls. Successful pattern transfer is realized by reactive ion etching using Cl (H) containing plasmas. CHF₃/Ar, C₂ClF₅/Ar, C₂ClF₅/Ar/O₂, SiCl₄, and CHCl₃ plasmas were used to etch GaN. The GaN etch rate is dependent on the crystalline quality of GaN. Higher crystalline quality GaN films exhibit slower etch rates than GaN films with higher dislocation and stacking fault density.     

Pt电极的磁增强反应离子刻蚀的研究

以SF6/O2作为刻蚀气体,用磁增强反应离子刻蚀(MERIE)技术,对磁控溅射法制备的Pt电极进行了刻蚀。结果表明:Pt的刻蚀速率与刻蚀气体的混合比率以及刻蚀功率都有一定关系。在相同功率下,R[O2∶(SF6+O2)]=2/6,刻蚀速率达到极大值,功率为120W时,刻蚀速率极大值为12.4nm/min。AFM分析表明,薄膜表面的粗糙度随刻蚀功率增加而变大,均方根粗糙度从120W时的0.164nm增加到160W时的0.285nm。经优化工艺参数刻蚀后的Pt电极图形结构平整,边缘整齐。